Makani Wind Energy Puts Composites on a Tether

by ccaldwell@fibreglast.com

Wind energy is more commercially available than ever, but still only accounts for less than 5% of energy production in the United States. This may be due, in part, because the affordability of wind power is limited by existing systems. While wind turbine structures have, in fact, been enabled to generate more power over time, they’ve only done so by becoming taller, heavier, and more expensive. And in order for clean energy sources like wind to gain mass adoption, they must become as affordable and available as traditional fossil fuels.

Wind energy power company Makani has developed an airborne wind turbine (AWT) that eliminates 90% of the material used in conventional wind systems. It operates on the same principles as a conventional wind turbine, but is tethered to the ground like a kite. The tether makes it possible to access more wind in more places at a lower cost. High-strength, low-weight composites, in particular carbon fiber, set the physics into motion.

The technology is unique. The AWT generates power through the tethered airfoil made from composites which is outfitted with turbines. The wing flies across the wind in large vertical circles at up to 1,000 feet altitude, where the wind is stronger and more consistent than the winds reached by conventional systems. As it circles, air moves across the rotors, forcing them to spin and driving a generator to produce electricity. Electricity travels down the tether, made from conductive wires, and into the grid.

The Makani also uses lift force—the lift in this case moves the wing forward and keeps it aloft. In periods of low wind, the rotors on board the wing are computer-powered to hover safely to the ground (much like a helicopter) and await proper conditions. During such conditions, or when the wing needs to be inactive, it is stowed at the top of the spar buoy or ground station.

Lack of wind power will likely not be an issue offshore, where Makani may focus for the future. Winds are stronger offshore, and about half the world’s population lives on the coast. If Makani AWTs could be launched from floating stations buoyed in the ocean, they could harness this increased power and minimize energy lost in transmission. At the same time, they could be flown far enough offshore to be out of sight and hearing range—both often concerns of coastal residents and business owners.

The Makani project has its critics and, based on the multitude of regulations already in place, it will have significant hurdles to maneuver before it becomes a viable option. It may, however, have one boost: Makani was acquired just over a year ago by Google X, Google’s company hatchery for big ideas like Google Glass and the driverless car. A lot of people are taking notice.